The invention relates to an air bag module for a motor vehicle steering wheel.
In a known steering wheel an air bag module of the aforementioned kind serves in all, or as part thereof, as a vibration damper, i.e. for suppressing unwanted vibrations excited by the chassis and transmitted into the steering wheel (DE 3925761 A1). For this purpose the air bag module or a part thereof is connected to the steering wheel in such a manner that a certain movement of the air bag module relative to the steering wheel is possible. The actual connecting means consist of rivets or bolts, elastic means being provided between the parts to be connected to each other, however, to ensure that no rigid connection results and that the air bag module, or a part thereof, is free to vibrate relative to the steering wheel and may thus be utilized as a vibration damper.
Experience has shown, however, that by the known elastic connection between air bag module and steering wheel only very small vibration amplitudes are achieved and that damping is effective only in a relative narrow-frequency range due to the ability of the elastic material employed to elastically deform being heavily restricted by the actual connecting means (rivets, bolts).
The invention provides an air bag module which utilizes the air bag module as a vibration damper in the steering wheel with the improvement that unwanted vibrations of the steering wheel are better suppressed.
The air bag module according to the invention for a motor vehicle steering wheel having a steering wheel axis comprises the following components: a gas bag, an inflator having a housing, a cover cap, an inflator support, an annular mounting plate arranged on the inflator support, and a mounting cylinder made of an elastic material and oriented parallel to the steering wheel axis. Further, means for interconnecting the components into the module are provided. The mounting cylinder has free rims connected, on the one hand, to the mounting plate and, on the other, to the inflator.
It is in this way that the inflator, representing the largest single mass of the air bag module, is connected solely via the mounting cylinder of elastic material to the remaining components of the air bag module and may thus be employed as a vibration damper. By suitable design and selection of material the mounting cylinder may be easily adapted to the various requirements so that the nuisance vibrations which differ from one type of vehicle to another are effectively suppressed. Doing away with other means of connecting the inflator to the mounting plate does not place restrictions on the design of the mounting cylinder which may thus be fully adapted to the requirements of the vibration system, apart from the strength needed for a reliable connection. By means of an auxiliary flange it can be assured that the inflator cannot be totally separated from the air bag module even if in the explosive-like inflation of the gas bag the reaction forces in accordance with the design were to be exceeded to such an extent that the mounting cylinder is destroyed. On the other hand, the mounting cylinder in accordance with the invention represents a component of relative simple design which takes up little space for installation and, in addition, may seal off the interior of the air bag from the environment so that no contamination is able to find its way into the air bag and no filling gases can escape in the case of activation.
The elastic mounting cylinder may further be fixed to a surrounding mounting flange connected to the housing of the inflator.